Path: dp-news.maxwell.syr.edu!spool.maxwell.syr.edu!drn.maxwell.syr.edu!news.maxwell.syr.edu!elnk-pas-nf1!newsfeed.earthlink.net!stamper.news.pas.earthlink.net!stamper.news.atl.earthlink.net!newsread2.news.atl.earthlink.net.POSTED!3ce9497d!not-for-mail Reply-To: "David Cressey" From: "David Cressey" Newsgroups: comp.databases.theory References: <1132207394.336133.241390@g44g2000cwa.googlegroups.com> <437c659a$1@news.fhg.de> <1132227541.584895.246870@o13g2000cwo.googlegroups.com> <437c77ee$1@news.fhg.de> <1132233342.792567.129540@g14g2000cwa.googlegroups.com> <437c85de$1@news.fhg.de> <1132237398.838820.240080@g47g2000cwa.googlegroups.com> <437c989a$1@news.fhg.de> <1132241343.741214.108550@g43g2000cwa.googlegroups.com> <437ca927$1@news.fhg.de> <1132246841.936501.150760@o13g2000cwo.googlegroups.com> Subject: Re: So what's null then if it's not nothing? Lines: 26 X-Priority: 3 X-MSMail-Priority: Normal X-Newsreader: Microsoft Outlook Express 5.50.4133.2400 X-MimeOLE: Produced By Microsoft MimeOLE V5.50.4133.2400 Message-ID: Date: Thu, 17 Nov 2005 22:39:50 GMT NNTP-Posting-Host: 4.154.204.161 X-Complaints-To: abuse@earthlink.net X-Trace: newsread2.news.atl.earthlink.net 1132267190 4.154.204.161 (Thu, 17 Nov 2005 14:39:50 PST) NNTP-Posting-Date: Thu, 17 Nov 2005 14:39:50 PST Organization: EarthLink Inc. -- http://www.EarthLink.net Xref: dp-news.maxwell.syr.edu comp.databases.theory:34427 "David Portas" wrote in message news:1132246841.936501.150760@o13g2000cwo.googlegroups.com... > Not at all the same thing because nulls violate the Information > Principle, which is a foundation of RM. Nulls as formulated in SQL also > create logical problems that are very hard to solve - at least SQL > hasn't succeeded in solving them very satisfactorily. Not according to Codd. > RM does not prohibit such questions. If it is more natural to give some > answer then the user can demand such an answer. The user can decide > what he wants to see in the case of a dog with colour or a dog without > colour. I would challenge your implication that users find nulls"more > natural". I bet most DBMS users wouldn't do a very good job of > explaining what a null is. In fact in many database projects the > developers go to a lot of trouble to hide nulls from regular users. And, in the real world, the user frequently deals with dogs that might or might not have color, and doesn't care about that.